An easier answer (religious) is ; Man is not supposed to know.
How do you mean that? Do you mean humans cannot know with finality? If so, that's a scientific stance, not a religious one. But maybe you meant he should just stop seeking at some point? Yeah, that'd be a religious and easier "answer".
The will-to-feeling-certain that many people suffer from is a tragic thing because it shuts down their curiosity. If a person would just say “I don’t know but I’m very curious” so that they buy or borrow some science books or take science classes at a community college, the joyous sense of wonder can only increase. Science doesn’t diminish the wonder at all, it adds more awe and mystery and wonder.
Others prefer to fill in the uncertain spaces with guesses. Then they assign their guesses the status of knowledge and get pissed if anyone doubts what marvels of inviolable certainty that their stupid guesses are. Or they memorize crap left over from medieval times. Or they float in a new-agey haze and mistake it for "open-mindedness". Sadly
it's easier to just form quick and easy opinions, or to memorize dogmas made by long-dead parochial sorts who didn't think the world was much worth looking at anyway, or skip learning cuz it's easy to be a "floater".
At any point that you arrive at “God” as an answer, you’ve projected some mental stuff upon your cave wall.
Again, science doesn’t diminish the mystery and wonder, it adds more:
(The speaker is the physicist Richard Feynman.)